Kidney Allocation Policy: Past, Present, and Future

Decreasing efficiency in deceased donor kidney offer notifications under the new distance-based kidney allocation system

Organ Procurement Organizations (OPOs) recover deceased donor kidneys and place them with matched recipients according to ranked match runs of patients, but offer notification practices differ across the OPOs and have changed following updates to allocation policy (kidney allocation system 250 [KAS250]). This national registry study used batch notification data to quantify time spent on kidney allocation and identify variations in batch notification practices across OPOs before and after the KAS250 allocation system era. Overall allocation time between the first and last offer notifications increased from a median of 1 to 7 hours under the KAS250 allocation system. For match runs of unplaced kidneys, allocation time increased from a median of 18 to 28 hours. Out-of-sequence (OOS) allocation, used by OPOs to limit nonutilization due to excess cold ischemia time, more than doubled in frequency between 2018 and 2022, with median time from first offer to initiation of OOS varying across OPOs from 0 to 47 hours. Increasing rates of organ nonutilization and the observed allocation practice differences based on organ quality demonstrate the urgent need for new approaches to achieve more efficient placement of hard-to-place kidneys. Data-driven approaches to optimize kidney allocation efforts will help ensure fairness in a system that currently allows for wide practice variation and frequent OOS allocation.

Inconsistent values and algorithmic fairness: a review of organ allocation priority systems in the United States

BACKGROUND

The Organ Procurement and Transplant Network (OPTN) Final Rule guides national organ transplantation policies, mandating equitable organ allocation and organ-specific priority stratification systems. Current allocation scores rely on mortality predictions.

METHODS

We examined the alignment between the ethical priorities across organ prioritization systems and the statistical design of the risk models in question. We searched PubMed for literature on organ allocation history, policy, and ethics in the United States.

RESULTS

We identified 127 relevant articles, covering kidney (19), liver (60), lung (24), and heart transplants (23), and transplant accessibility (1). Current risk scores emphasize model performance and overlook ethical concerns in variable selection. The inclusion of race, sex, and geographical limits as categorical variables lacks biological basis; therefore, blurring the line between evidence-based models and discrimination. Comprehensive ethical and equity evaluation of risk scores is lacking, with only limited discussion of the algorithmic fairness of the Model for End-Stage Liver Disease (MELD) and the Kidney Donor Risk Index (KDRI) in some literature. We uncovered the inconsistent ethical standards underlying organ allocation scores in the United States. Specifically, we highlighted the exception points in MELD, the inclusion of race in KDRI, the geographical limit in the Lung Allocation Score, and the inadequacy of risk stratification in the Heart Tier system, creating obstacles for medically underserved populations.

CONCLUSIONS

We encourage efforts to address statistical and ethical concerns in organ allocation models and urge standardization and transparency in policy development to ensure fairness, equitability, and evidence-based risk predictions.

Identifying when racial and ethnic disparities arise along the continuum of transplant care: a national registry study

Background

Fewer minoritized patients with end-stage kidney disease (ESKD) receive kidney transplantation (KT); efforts to mitigate disparities have thus far failed. Pinpointing the specific stage(s) within the transplant care continuum (being informed of KT options, joining the waiting list, to receiving KT) where disparities emerge among each minoritized population is pivotal for achieving equity. We therefore quantified racial and ethnic disparities across the KT care continuum.

Methods

We conducted a retrospective cohort study (2015-2020), with follow-up through 12/10/2021. Patients with incident dialysis were identified using the US national registry data. The exposure was race and ethnicity (Asian, Black, Hispanic, and White). We used adjusted modified Poisson regression to quantify the adjusted prevalence ratio (aPR) of being informed of KT, and cause-specific hazards models to calculate adjusted hazard ratios (aHR) of listing, and transplantation after listing.

Findings

Among 637,951 adults initiating dialysis, the mean age (SD) was 63.8 (14.6), 41.8% were female, 5.4% were Asian, 26.3% were Black, 16.6% were Hispanic, and 51.7% were White (median follow-up in years [IQR]:1.92 [0.97-3.39]). Black and Hispanic patients were modestly more likely to be informed of KT (Black: aPR = 1.02, 95% confidence interval [CI]:1.01-1.02; Hispanic: aPR = 1.03, 95% CI: 1.02-1.03) relative to White patients. Asian patients were more likely to be listed (aHR = 1.18, 95% CI: 1.15-1.21) but less likely to receive KT (aHR = 0.56, 95% CI: 0.54-0.58). Both Black and Hispanic patients were less likely to be listed (Black: aHR = 0.87, 95% CI: 0.85-0.88; Hispanic: aHR = 0.85, 95% CI: 0.85-0.88) and receive KT (Black: aHR = 0.61, 95% CI: 0.60-0.63; Hispanic: aHR = 0.64, 95% CI: 0.63-0.66).

Interpretation

Improved characterization of the barriers in KT access specific to each racial and ethnic group, and the interventions to address these distinct challenges throughout the KT care continuum are needed; our findings identify specific stages most in need of mitigation.

Funding

National Institutes of Health.

Kidney Transplant Candidacy: Addressing Common Medical and Psychosocial Barriers to Transplant

Improving access to kidney transplants remains a priority for the transplant community. However, many medical, psychosocial, geographic, and socioeconomic barriers exist that prevent or delay transplantation for candidates with certain conditions. There is a lack of consensus regarding how to best approach many of these issues and barriers, leading to heterogeneity in transplant centers' management and acceptance practices for a variety of pretransplant candidate issues. In this review, we address several of the more common contemporary patient medical and psychosocial barriers frequently encountered by transplant programs. The barriers discussed here include kidney transplant candidates with obesity, older age, prior malignancy, cardiovascular disease, history of nonadherence, and cannabis use. Improving understanding of how to best address these specific issues can empower referring providers, transplant programs, and patients to address these issues as necessary to progress toward eventual successful transplantation.

Highly Sensitized Kidney Transplant Outcomes After the 2014 Kidney Allocation System Change

Introduction: Kidney Allocation System (KAS) was implemented by United Network for Organ Sharing in 2014 to reduce allocation disparities. Research Questions: Outcomes of highly sensitized patients (calculated panel reactive antibody (cPRA) ≥ 97%) before and after KAS were compared to low-risk recipients (cPRA <10%) in the post-KAS era were examined. The impact on racial disparities was determined. Design: This was a retrospective study of national registry data. Two cohorts of adult candidates waitlisted for deceased donor transplantation during 3-year periods before and after KAS were identified. Results: Highly sensitized patients (N = 1238 and 4687) received a deceased donor kidney transplant between January 1, 2011 and December 31, 2013 and between January 1, 2015 and December, 31, 2017. Racial disparity for highly sensitized patients improved, yet remained significant (P < 0.001), with Black patients comprising 40% and 41% of the highly sensitized candidates and 28% and 34% of the recipients pre- and post-KAS. While posttransplant death-censored graft failure for highly sensitized recipients was similar overall, post-KAS was associated with improved graft survival in the first year after transplant (HR 0.56, 95% CI 0.40-0.78). When compared to contemporaneous lowrisk recipients, both death-censored and all-cause graft failure were similar for highly sensitized recipients and was associated with increased risk for death-censored graft failure beyond the first year (HR 1.39, 95% CI 1.11-1.73). Conclusion: The allocation system led to an increase in transplantation in highly sensitized candidates without compromising outcomes. Although KAS has led to more balanced transplant rates between highly sensitized Black and White patients, racial inequalities persist.

Comparison Between Black Non-Hispanic and White Non-Hispanic Simultaneous Pancreas-Kidney Transplant Candidates and Recipients

INTRODUCTION

This study examined simultaneous pancreas-kidney transplant (SPKt) in Black and White patients to identify disparities in transplantation, days on the waitlist, and reasons for SPKt waitlist removal.

METHODS

Using the United Network for Organ Sharing Standard Transplant Analysis and Research file, patients between January 1, 2009, and May 31, 2021, were included. Three cohorts (overall, SPKt recipients only, and those not transplanted) were selected using propensity score matching. Conditional logistic regression was used for categorical outcomes. Days on the waitlist were compared using negative binomial regression.

RESULTS

Black patients had increased odds of receiving a  SPKt (OR, 1.25 [95% CI, 1.11-1.40], p < 0.001). White patients had increased odds of receiving a kidney-only transplant (OR 0.48 [95% CI, 0.38-0.61], p < 0.001), and specifically increased odds of receiving a living donor kidney (OR 0.34 [0.25-0.45], p < 0.001).

CONCLUSION

This study found that Black patients are more likely to receive a SPKt. Results suggest that there are opportunities for additional inquiry related to patient removal from the waitlist, particularly considering White patients received or accepted more kidney-only transplants and were more likely to receive a living donor kidney-only transplant.

Outcomes of Deceased Donor Kidney Recipients From the Same Donor Based on Donor-Recipient Sex Discordance

INTRODUCTION

Outcomes of deceased donor kidney transplant (DDKT) recipients from the same donor with donor-recipient sex discordance have been studied with inconsistent results.

METHODS

Adult DDKT where both kidneys from the same donor occurred at our center in two different recipients of different sexes were included. Outcomes were analyzed separately for male and female donors, based on the concordance or discordance between donor-recipient sex: Male-male (M-m) versus Male to female (M-f) or vice versa, F-f versus F-m. Acute rejection (AR) and uncensored graft failure were primary outcomes of interest. The univariate and multivariate risks for AR and graft failure were conducted using the Cox proportional hazards model and log-rank tests.

RESULTS

A total of 130 donors, 84 male and 46 female fulfilled our selection criteria and were transplanted in 260 recipients. With respect to the concordant groups (M-m or F-f), sex discordance was not significantly associated with the risk of rejection in multivariate analysis (M-f vs. M-m HR 1.15 [0.53-2.53, P = 0.72]; F-m vs. F-f HR 1.77 [0.71-4.39, P = 0.23]). Sex discordance was also not significantly associated with graft failure in multivariate analysis. Interestingly, risk factors for AR differed among male donors and female donors. The higher calculated panel reactive antibodies (cPRA) and nonwhite recipients were at increased risk for AR in F-m, but not in M-f.

CONCLUSIONS

Donor-recipient sex discordance was not significantly associated with AR or graft failure. Risk factors for AR may differ across male and female donors.

Validation of the kidney donor profile index (KDPI) for deceased donor kidney transplants in China

BACKGROUND

The kidney donor profile index (KDPI) evaluates kidney donor's age, height, weight, ethnicity, cause of death, high blood pressure, diabetes, exposure to hepatitis C and estimated glomerular filtration (eGFR). Kidneys with lower KDPI scores are expected to function longer that those with higher KPDI values. The applicability of KDPI score in Chinese kidney transplant donation has not yet been validated. This study evaluated the prognostic value of KDPI score in Chinese kidney transplant patients.

METHODS

A retrospective analysis was conducted on 184 deceased donors and 353 corresponding kidney transplant patients at the Organ Transplantation Department of Renmin Hospital of Wuhan University between 2018 and 2021. The donors and recipients were stratified into four groups based on their KDPI score: KDPI 85-100, KDPI 60-84, KDPI 21-59, and KDPI 0-20.

RESULTS

As expected, the KDPI 85-100 group was associated with a poor short-term renal function (both postoperative creatinine and eGFR with P > 0.05), a higher incidence of delayed graft function (DGF; 25.5% for KDPI 85-100 group vs. 10.2% for KDPI 60-84 group vs. 5.4% for KDPI 21-59 group vs. 0 for KDPI 0-20 group, all P > 0.05). Furthermore, the same groups showed worse 3-year patient survival rate: 86.3% for KDPI 85-100 group vs. 97.01% for KDPI 60-84 group vs. 97.83% for KDPI 21-59 group vs. 100% for KDPI 0-20 group, all P > 0.05); and renal survival rate: 82.6% for KDPI 85-100 group vs. 92.99% KDPI 60-84 group vs.97.83% for KDPI 21-59 group vs. 100% for KDPI 0-20 group, all P > 0.05). Our analysis showed that the KDPI score had a good predictive value for the survival of kidney transplants and patients in our center (area under the curve: 0.728 and 0.76, P > 0.05).

CONCLUSION

We recommend that the KDPI scoring system can be employed as an effective tool to predict kidney transplantation outcomes in deceased donation in China.

Equity matrix for kidney transplant allocation

There is a general agreement that the distribution of kidneys for transplantation should balance utility criteria with justice. Moreover, a kidney allocation system must be based on transparent policies and seen as an ongoing process. This study aims to present an allocation system grounded on an equity matrix that balances the criteria of utility and justice. Synthetic data for a waiting list with 2000 transplant candidates and a pool of 280 donors were generated. A color priority system, the Eurotransplant (ET) kidney allocation system, and the proposed Equity Matrix (EQM) allocation system were compared after 1000 iterations of kidney allocations. Distributions of variables like the age difference, Human Leukocyte Antigens (HLA) mismatches (mmHLA), recipients' time on dialysis, cPRA, and a transplant score obtained by different allocation models were compared graphically and with Cohen's d effect size. For the analyzed variables, when we compare only the selected recipients from ET with the selected recipients from the EQM neutral model, we can conclude that the former model selects more hypersensitized recipients, a higher number of 65+ years' old recipients with 65+ years' old donors and higher number of recipients with 0 mmHLA. While recipients from EQM neutral are slightly older, have a lower age difference with their donors, have a lower number of mmHLA, are less likely to have 6 mmHLA with their donors, and have more time on dialysis. The proposed EQM model attempts to provide a simple, transparent, and equitable response to a complex question with results that outperform established practices.

Evolving Trends in Kidney Transplant Outcomes Among Older Adults: A Comparative Analysis Before and During the COVID-19 Pandemic

Background

Advancements in medical technology, healthcare delivery, and organ allocation resulted in improved patient/graft survival for older (age ≥65) kidney transplant (KT) recipients. However, the recent trends in these post-KT outcomes are uncertain in light of the mounting burden of cardiovascular disease, changing kidney allocation policies, heterogeneity in candidates' risk profile, and the coronavirus disease 2019 pandemic. Thus, we examined secular trends in post-KT outcomes among older and younger KT recipients over the last 3 decades.

Methods

We identified 73 078 older and 378 800 younger adult (aged 18-64) recipients using Scientific Registry of Transplant Recipients (1990-2022). KTs were grouped into 6 prepandemic eras and 1 postpandemic-onset era. Kaplan-Meier and Cox proportional hazards models were used to examine temporal trends in post-KT mortality and death-censored graft failure.

Results

From 1990 to 2022, a 19-fold increase in the proportion of older KT recipients was observed compared to a 2-fold increase in younger adults despite a slight decline in the absolute number of older recipients in 2020. The mortality risk for older recipients between 2015 and March 14, 2020, was 39% (adjusted hazard ratio [aHR] = 0.61, 95% confidence interval [CI], 0.50-0.75) lower compared to 1990-1994, whereas that for younger adults was 47% lower (aHR = 0.53, 95% CI, 0.48-0.59). However, mortality risk during the pandemic was 25% lower (aHR = 0.75, 95% CI, 0.61-0.93) in older adults and 37% lower in younger adults (aHR = 0.63, 95% CI, 0.56-0.70) relative to 1990-1994. For both populations, the risk of graft failure declined over time and was unaffected during the pandemic relative to the preceding period.

Conclusions

The steady improvements in 5-y mortality and graft survival were disrupted during the pandemic, particularly among older adults. Specifically, mortality among older adults reflected rates seen 20 y prior.

Maximizing opportunities for kidney transplantation in older adults

PURPOSE OF REVIEW

To summarize the current state of evidence related to the outcomes of older adults who need and receive kidney transplants, and strategies to facilitate appropriate transplant access in this at-risk group.

RECENT FINDINGS

Older adults are a rapidly growing subgroup of the kidney transplant waitlist. Compared to younger adults, older kidney transplant recipients have increased mortality after kidney transplant and lower death-censored graft survival. In determining suitability for transplantation in older patients, clinicians must balance procedural and immunosuppression-related risk with incremental survival when compared with dialysis. To appropriately increase access to transplantation in this population, clinicians and policy makers consider candidates' chronological age and frailty, as well as the quality of and waiting time for a donated allograft. Given risk of deterioration prior to transplant, candidates should be rapidly evaluated, listed, and transplanted using living donor and or less than ideal deceased donor organs when available.

SUMMARY

Access to transplantation for older adults can be increased through targeted interventions to address frailty and reduce waiting times through optimized organ use. Focused study and educational interventions for patients and providers are needed to improve the outcomes of this vulnerable group.

Waiting-List and early posttransplant prognosis among ethnoracial groups: Data from the organ procurement and transplantation network

Background

Racial/ethnic disparity in waiting-list mortality among candidates listed for kidney transplantation (KT) in the United States remains unclear. We aimed to assess racial/ethnic disparity in waiting-list prognosis among patients listed for KT in the United States in the current era.

Methods

We compared waiting-list and early posttransplant in-hospital mortality or primary nonfunction (PNF) among adult (age ≥18 years) white, black, Hispanic, and Asian patients listed for only KT in the United States between July 1, 2004 and March 31, 2020.

Results

Of the 516,451 participants, 45.6%, 29.8%, 17.5%, and 7.1% were white, black, Hispanic, and Asian, respectively. Mortality on the 3-year waiting list (including patients who were removed for deterioration) was 23.2%, 16.6%, 16.2%, and 13.8% in white, black, Hispanic, and Asian patients, respectively. The cumulative incidence of posttransplant in-hospital death or PNF after KT was 3.3%, 2.5%, 2.4%, and 2.2% in black, white, Hispanic, and Asian patients,respectively. White candidates had the highest mortality risk on the waiting list or of becoming too sick for a transplant, while black (adjusted hazard ratio, [95% confidence interval, CI], 0.67 [0.66-0.68]), Hispanic (0.59 [0.58-0.60]), and Asian (0.54 [0.52-0.55]) candidates had a lower risk. Black KT recipients (odds ratio, [95% CI] 1.29 [1.21-1.38]) had a higher risk of PNF or death before discharge than white patients. After controlling confounders, black recipients (0.99 [0.92-1.07]) had a similar higher risk of posttransplant in-hospital mortality or PNF as white patients than Hispanic and Asian counterparts.

Conclusions

Despite having a better socioeconomic status and being allocated better kidneys, white patients had the worst prognosis during the waiting periods. Black recipients and white recipients have higher posttransplant in-hospital mortality or PNF.

Deceased Donor Characteristics and Kidney Transplant Outcomes

Kidney transplantation is the therapy of choice for people living with kidney failure who are suitable for surgery. However, the disparity between supply versus demand for organs means many either die or are removed from the waiting-list before receiving a kidney allograft. Reducing unnecessary discard of deceased donor kidneys is important to maximize utilization of a scarce and valuable resource but requires nuanced decision-making. Accepting kidneys from deceased donors with heterogenous characteristics for waitlisted kidney transplant candidates, often in the context of time-pressured decision-making, requires an understanding of the association between donor characteristics and kidney transplant outcomes. Deceased donor clinical factors can impact patient and/or kidney allograft survival but risk-versus-benefit deliberation must be balanced against the morbidity and mortality associated with remaining on the waiting-list. In this article, the association between deceased kidney donor characteristics and post kidney transplant outcomes for the recipient are reviewed. While translating this evidence to individual kidney transplant candidates is a challenge, emerging strategies to improve this process will be discussed. Fundamentally, tools and guidelines to inform decision-making when considering deceased donor kidney offers will be valuable to both professionals and patients.